Developing Environmentally Sound Poultry Litter Management Practices for Sustainable Cropping Systems

Final Report for LS92-048

Project Type: Research and Education
Funds awarded in 1992: $140,000.00
Projected End Date: 12/31/1995
Matching Non-Federal Funds: $116,669.00
Region: Southern
State: Texas
Principal Investigator:
D. R. Earhart
Texas Agricultural Experiment Station
Expand All

Project Information

Abstract:

[Note to online version: The report for this project includes special characters that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact Southern SARE at (770) 412-4787 or sare@griffin.uga.edu.]

Many broiler enterprises produce excess manure for environmentally safe recycling in cropping systems on available land under their control. Application rates and frequencies are often excessive. Including cover crops in rotational cropping systems, such as vegetables followed by grass forage for temporary grazing, hay, or silage, may enable producers to apply litter at higher rates more frequently, and reduce nutrient losses due to runoff.

The objectives of this study are: (1) evaluate the environmental and economic impact of broiler litter application rates and frequencies on selected vegetables; (2) investigate the feasibility of growing warm and cool season annual forage crops in rotational cropping systems to remove excess nutrients supplied by poultry litter; (3) determine nutrient loss due to runoff in a vegetable, forage, litter management system; (4) demonstrate litter management practices on grower owned land under grower conditions.

The litter rates applied for all objectives were based on soil test nitrogen (N) requirement of the crop and percent N content of the litter. Treatments were incorporated immediately after application by power tilling.

In objective 1, litter was applied at the recommended rate or at two or four times the recommended rate and either all pre-plant or half pre-plant and half side-dressed. Throughout the study, sweet corn was the spring crop followed by broccoli in the fall. Data were collected on crop yield, nutrient uptake, nutrient accumulation, and nutrient leaching. This study indicates that producers could apply all the litter preplant or in split application without affecting growth or yield of either the spring or fall crop.

Increasing litter application at more than twice the recommended rate decreased yield. Applying litter in excess of the recommended rate increases the risk of nitrate leaching into ground water. Regardless of rate applied, phosphorus (P) continued to increase in the surface 6 in. of soil. This suggests that non-point source pollution of surface waters might occur after years of continued applications of litter on sandy soils. Continuous litter application rates greater than recommended causes a subsequent increase in K concentration in the surface 1 ft. of soil which can lead to negative effects on soil salinity and lower availability of magnesium. There is little effect from litter rate increase on Mg and Ca concentration in the surface 1 ft. but does increase Ca at depths below 3 ft. Litter rate increase does not significantly effect soil pH. Neither litter rate or fertilizer blend caused any detrimental salt accumulation.

Treatments in objective 2 consisted of cropping system (spring veg.-fall veg., spring forage-fall veg., spring veg.-fall forage) with litter applied at either recommended two times the recommended rate. Litter was applied in the spring, fall, or spring and fall. Tomatoes were the spring vegetable crop followed by turnips in the fall. Sorghum-sudan was the spring forage crop with Elbon rye planted in the fall. Data were collected on yield, nutrient uptake, nutrient accumulation and leaching. This study showed litter applications in both spring and fall increased yields of vegetable and forage crop. Producers utilizing a system of spring vegetables followed by fall forage could reduce leaching of nitrogen through the soil profile as well as reduce phosphorus accumulation in the surface 6 in. of soil. Applying litter rates sufficient to meet crop needs for N, regardless of cropping system or season of application, results in P accumulation that can lead to non-point source pollution of surface water. None of the cropping systems studied had any significant effect on K or Ca. All cropping systems reduced Mg concentration at all soil depths while reducing soil pH in the surface 1 ft. A cropping system of spring vegetables followed by a fall cover crop reduces salt accumulation and leaching.

Regardless of the season in which litter is applied K, Ca, and Mg concentration as well as soil pH decreases over time. Applying litter and commercial blend fertilizer in both spring and fall tends to increase salt accumulation and leaching below 1 ft.

In objective 3, cropping systems of spring vegetable-fall forage, spring vegetable-fall fallow, and spring vegetable-fall vegetable were studied. Fertility treatments consisting of a control, the recommended litter rate, four times the recommended rate, and a commercial blend were applied. The spring vegetable crop was sweet corn followed by broccoli in the fall. Sorghum-sudan was the spring cover crop. Elbon rye was seeded in the fall. Data were obtained on NO3-N and P accumulation, leaching, and runoff. The data indicated that a system of spring vegetables followed by a fall forage could reduce leaching and accumulation of N. Leaving the soil fallow in the fall increased NO3-N leaching. Regardless of cropping system used P will continue to increase in the surface 1 ft. of soil. A system of spring vegetables followed by fall cover greatly reduced the amount of NO3-N in the soil solution. Very little NO3-N and almost undetectable amounts of P were found in runoff water. This would indicate that incorporation of litter, which would be a normal practice under row crop production, would greatly reduce the chance of surface water pollution.

Demonstrations of litter use in vegetable production has increased grower awareness of this valuable nutrient source. Several are beginning to utilize this nutrient source in their operations. One grower in particular utilized litter in his intensive watermelon production program (mulch, drip irrigation) and realized yields of approximately 72,000 lbs/ac. Another producer of greens and onions, has begun incorporating poultry litter into his fertility program. A poultry producer diversified his operation by utilizing excess litter in a vegetable production program that supplies a local grocery chain with year round vegetables as well as a roadside stand market.

Studies in Texas and Oklahoma were established in 1992 to evaluate utilization of poultry litter in vegetable production systems. Three replicated studies were established at The Texas A&M University Research and Extension Center at Overton, and at Oklahoma State University Vegetable Research Station at Bixby. These studies consisted of: (1) evaluation of poultry litter rate and frequency of application on vegetables (Texas); (2) feasibility of growing warm- and cool-season annual forage crops to remove excess nutrients supplied by litter in rotational cropping, vegetable systems (Texas-Oklahoma); (3) evaluate runoff and leaching in vegetable-forage litter management systems (Texas); (4) demonstrate litter use in vegetable production systems on grower owned land under grower conditions (Texas-Oklahoma). In all studies litter rates were based on N requirement of the crop and percent N in the litter. Rates were compared to fertilizer blends and a 0 check. Frequency of application of litter (total, split) had no significant effect on yield of vegetables. Increasing litter application to more than twice the recommended rate decreased yield as well as increased the risk of NO3-N leaching and accumulation at lower depths of the soil profile. A system of spring vegetables followed by fall forage reduced leaching of NO3-N through the soil profile and the amount in the soil solution. Regardless of the cropping system, very little NO3-N and almost undetectable amounts of P were found in runoff water. This would indicate that incorporation of litter would greatly reduce the chance of surface water pollution. Phosphorus accumulation increased in the surface 30 cm (1 ft) of soil each season regardless of cropping system or time of application. As litter rate increased, P accumulation increased accordingly. Accumulation of P from fertilizer blend treatments was found to be significantly less than from poultry litter. Due to demonstrations of litter use in vegetable production programs, grower interest and awareness of the nutrient value of poultry litter has been augmented.

Project Objectives:

The objectives of this study were to: (1) evaluate the environmental and economic impact of broiler litter application rates and frequencies on selected vegetable crops; (2) investigate the feasibility of growing warm and cool season annual forage crops in rotational-cropping, vegetable systems to remove excess nutrients supplied by poultry litter; (3) determine nutrient loss due to runoff in a vegetable, forage, litter management system; and (4) demonstrate litter management practices on grower owned land under grower conditions.

Introduction:

More than 5.5 billion broilers produced in the U.S. in 1989 created over 32.6 million metric tons of dry manure (15). Most mineral elements essential for plant growth are found in broiler litter (12,13,18). Application of 22.4 t of 30% moisture poultry litter per hectare can supply approximately 645 kg N, 227 kg P, 342 kg potassium (K), 127 kg calcium (Ca), and 28 kg magnesium (Mg), with trace amounts of iron (Fe), manganese (Mn), zinc (Zn), boron (B), and molybdenum (Mo) (13). Litter can supply adequate amounts of P and K for most plant growth needs (14). Safe loading rates of poultry manure in intensive vegetable cropping programs have not been determined. Present recommended application rates are based on requirements which vary by crop, chemical composition of litter, and the residual level of available nutrients in the soil (7). Litter contains approximately 4% N on a dry weight basis (2). This N is the major component for determining application rates and can be lost through volatilization and leaching (1).

Soil incorporation of manure is preferable to surface application for most cultivated crops (6, 9). Unincorporated litter loses from 50 to 70% of its total N through volatization (18). Broadcast incorporated litter increased plant P, K, and Mg in watermelon when compared to commercial fertilizer, and produced statistically equal yields (3. 4). In a second year study where residual fertilizer was compared to additional applications equal to the previous year’s rate, poultry litter significantly increased watermelon leaf fresh and dry weights, vine length, yield, and average melon weight (5).

Manure supplied nutrients can accumulate and become detrimental to plant growth at high application rates (8, 16). Such conditions increase the risk of pollution and the movement of nutrients, especially NO3-N, into surface water and soil water percolate. Concentrations of P and K in litter increase soil P and K levels and may lead to imbalances with other nutrients (18). Approximately 30 to 50 kg of P/ha and 150 to 200 kg K/ha can be removed by high yielding warm season annuals (11). Cool season annuals can remove from 2.4 to 12.5 kg of P and 46 to 61 kg of K based on dry matter content at normal yield levels (10). Interseeded rye in Coastal bermudagrass increased total forage yield and reduced NO3-N losses to percolating soil water (19). Forage production reduced nutrient loss due to runoff (17).

Broiler production is increasing in many areas of the South (7, 15, 18). Expanded production increases the amount of poultry litter requiring disposal in a timely, profitable, and environmentally sound manner. High value crops such as vegetables can be incorporated into low-input sustainable production systems using broiler litter as a fertilizer. These systems enable broiler producers to diversify their operations with profitable alternatives.

Producers not interested in diversification can supplement their income by supplying litter to other agricultural production systems and urban ecosystems (ornamental/lawn/garden). The more that is known about litter value in production systems, the more price discovery is facilitated in the market place. Research is needed to identify poultry litter application strategies aimed at reducing nutrient concentrations in surface run-off, NO3- pollution of run-off and ground water, and soil nutrient imbalances. Application rates and frequencies must be evaluated before developing management plans for litter use in vegetable production systems.

Many broiler enterprises produce excess manure for environmentally safe recycling in cropping programs on available land under their control. Application rates and frequencies are often excessive. Including cover crops in rotational cropping systems, such as vegetables followed by grass forage for temporary grazing, hay, or silage, may enable producers to apply litter at higher rates more frequently, and reduce nutrient loss due to runoff. There is little data on the efficiency with which warm and cool season annuals remove nutrients supplied by litter.

Research

Materials and methods:

Factored experiments designed to evaluate the objectives were established at the Texas A&M University Agricultural Research and Extension Center, Overton, and Oklahoma State University Vegetable Research Station, Bixby, beginning in spring 1992. Soil sub-samples were obtained at random 15 cm (6 in) depths. These were combined into a composite for each area to be used for establishing objectives 1 through 3. The samples were analyzed by the Texas A&M University Soil Testing Lab and Oklahoma State Soil Test Lab for fertilizer recommendations.

Poultry litter was obtained and analyzed for N, P, K and moisture content. Litter was applied according to percent N, moisture content and recommendation for maximum crop yield based on N. This was considered the 1X rate. Inorganic rates were based on recommendations for N-P-K. Treatments applied by hand were either total before planting or one-half before planting and one-half at sidedress. All treatments were incorporated using a power tiller. The split applications were incorporated by a rolling cultivator. Plot integrity was maintained through the duration of the study. Plant and soil samples were dried and prepared for chemical analysis by standard laboratory procedures.

OBJECTIVE 1: Frequency X Litter Rate

Location: TAES-Overton.

Nine treatments were evaluated for two years in a split-plot design experiment with three replications of each treatment. The whole plot was frequency of application (total, split). Rate was the sub-plot (0, 1X, 2X, 4X). The whole plot dimension was 4 m by 6 m. Individual sub-plots consisted of four rows spaced 102 cm apart. Plot ends were separated by 0.9 m alleys.

Sweet corn (`Merit’) was used as the spring crop and broccoli (`Green Valiant’) as the fall crop for both years. Data were obtained from two middle rows on crop growth, quality, yield, plant nutrient levels, leaching and accumulation of mobile ions, and soil reaction.

In spring 1992, treatments were applied to plots on 9 April. The 1X rate was 10.9 Mg/ha (4.8 tons/ac). A fertilizer blend of 23.8N-4.3P-4.1K was applied for comparison. Sweet corn was seeded on 21 April and harvested on 7 and 15 July. Soil samples were obtained on 27 July.

In fall 1992, treatments were applied on 1 Sept. and broccoli transplanted on 4 Sept. The 1X rate was 8.7 Mg/ha (3.9 tons/ac). Fertilizer blend of 40.0N-5.24P-4.98K kg/ha was applied for comparison. Broccoli transplants were hand-planted on 4 Sept. and spaced 30 cm apart in the row. Harvest began on 17 Nov. and was completed on 3 Dec. Soil samples were obtained in March.

In spring 1993, treatments were applied to plots on 12 April. The 1X rate was 5.2 Mg/ha (2.3 tons/ac). A fertilizer blend of 33.6N-12.5P-46.6K kg/ha was applied for comparison. Sweet corn was seeded on 16 April and harvested on 29 June. Soil samples were obtained on 14 July.

In fall 1993, treatments were applied to plots on 15 Oct. The 1X litter rate was 9.3 Mg/ha (4.1 tons/ac). A fertilizer blend of 28.0N-7.3P-51.1K kg/ha was applied for comparison. Broccoli plants were hand transplanted on 27 Oct. Plots were harvested on 3 Jan. Soil samples were obtained on 6 Jan.

OBJECTIVE 2: Cropping System X Litter Rate X Time of Application.

Location: TAES-Overton, OSU-Bixby.

Texas: Twenty-one treatments were evaluated in a split-plot design with 3 replications of each. The whole plot was crop (spring veg.-fall veg., spring forage-fall veg., spring veg.-fall forage) with litter rate (0, 1X, 2X), and time of application (spring, fall, spring and fall) as sub-plots. Individual plot dimensions were the same as objective 1. Rates of litter and fertilizer blend were based on the same criteria as in objective 1. Tomatoes were the spring vegetable crop and turnips were seeded in the fall. Sorghum-sudan was the spring cover crop and Elbon rye was seeded in the fall. Data were obtained on yield, nutrient uptake, and nutrient accumulation and leaching. Plant and soil samples were dried at 600 C and prepared for chemical analysis by standard laboratory procedures.

METHODS: Texas, Spring 1992.

Treatments were applied to plots on 9 April. The 1X litter rate for tomato production was 8.2 Mg/ha (3.6 tons/ac) and sorghum-sudan 18.1 Mg/ha (8 tons/ac). Litter rates for tomato and sorghum-sudan production were compared to a fertilizer blend of 18.0N-5.7P-9.2K, and 20.6N-10.3P-10.3K kg/ha respectively.

Tomato transplants were hand-planted 46 cm apart in the row on two rows spaced 3 m apart on 16 April. Plants were staked and tied during the growing season. Tomatoes were harvested 22, 25, and 29 June.

Sorghum-sudan was drilled at 67.3 kg/ha 4 May. Plots were harvested with a HAGE 211B forage plot harvester on 15 June and 14 July. Sub-samples were obtained from each harvest for chemical analysis. Soil samples were collected on 30 July for all treatments.

METHODS: Texas, Fall 1992.

Treatments were applied to plots on 31 Aug. The 1X litter rate for turnip green production was 5.0 Mg/ha (2.2 tons/ac), and Elbon rye 9.2 Mg/ha (4.1 tons/ac). Litter rates for both crops were compared to a fertilizer blend of 22.0N-13.1P-24.9K and 20.0N-2.1P-7.5K kg/ha respectively.

Turnips were seeded two rows per bed with a push type seeder at a rate of 2.2 kg/ha on 8 Sept. Plots were harvested on 20 Oct.

Elbon rye was drilled on 25 Sept at 89.7 kg/ha seeding rate. Plots were harvested using a HAGE 211B forage plot harvester on 17 Nov. and 14 Sept.1993. Soil samples were obtained on 26 March 1993 for all treatments.

METHODS: Texas, Spring 1993.

Treatments were applied to plots on 22 April. The 1X litter rate for tomatoes was 5.1 Mg/ha (2.3 tons/ac) and sorghum-sudan 7.8 Mg/ha (3.5 tons/ac). Fertilizer blend was applied at rates of 20.2N-12.2P-93.0K and 28.0N-2.5P-60.5K kg/ha for tomatoes and sorghum-sudan respectively.

Tomatoes were transplanted on 23 April and harvested on 12 and 21 July. Sorghum-sudan was seeded on 10 May and harvested on 16 June and 6 July.

Soil samples were obtained on 9 Aug. for all treatments.

METHODS: Texas, Fall 1993.

Treatments were applied to plots on 15 Sept. The 1X litter rate for turnips was 5.9 Mg/ha (2.6 tons/ac) and rye 2.0 Mg/ha (0.9 tons/ac). Fertilizer blend was applied at rates of 63.9N-24.4P-111.6K and 18.7N-12.2P-69.5K kg/ha for turnips and rye respectively.

Turnips were seeded on 28 Sept. and harvested on 15 Nov. Elbon rye was seeded on 30 Sept. and harvested on 22 Nov. and 6 Dec. Soil samples were obtained on 21 Dec. for all treatments.

METHODS: Texas, Spring 1994.

Treatments were applied to plots on 16 March. The 1X litter rate for tomatoes was 4.5 Mg/ha (2.0 tons/ac) and sorghum-sudan 6.5 Mg/ha (2.9 tons/ac). Fertilizer blend was applied at rates of 30.0N-31.7P-83.7K and 50.4N-12.4P-65.1K kg/ha for tomatoes and sorghum-sudan, respectively.

Tomato plants were transplanted on 18 April and harvested on 22, 28 June and 5, 8, 11 July. Sorghum-sudan was seeded on 25 April and harvested on 2 June and 19 July. Soil samples were obtained on 25 July for all treatments.

METHODS: Texas, Fall 1994.

Treatments were applied to plots on 20 Sept. The 1X litter rate for turnips was 3.1 Mg/ha (1.4 tons/ac) and rye 2.4 Mg/ha (1.1 tons/ac). Fertilizer blend was applied at rates of 15.0N-112.2P-79.0K and 24.3N-9.7P-69.7K kg/ha for turnips and rye, respectively.

Turnips were seeded on 22 Sept. and harvested on 17 Nov. Elbon rye was seeded on 4 Oct. and harvested on 22 Nov. and 6 Dec. Soil samples were obtained on 8 Dec. for all plots.

METHODS: Oklahoma.
See attachment-Oklahoma Report.

OBJECTIVE 3: Leaching and Runoff.

Location: TAES-Overton.

In fall 1992, individual 4 m x 6 m plots were established in a split-plot design with three replications. Cropping system was the whole plot with litter rate as the sub-plot. A blend of commercial fertilizer was included for comparison. Sub-plots were separated by 20 cm, vertically installed, metal strips to prevent cross contamination between treatments. Each tier of whole plots was separated by 8 m alleys. Vacuum extraction tubes, for determining nutrient loss in the soil solution, were placed in each sub-plot to a depth of 122 cm. Graded troughs lined with 6-ml black plastic were established at the ends of selected sub-plots and connected to Parshall flumes with throat widths of 7.6 cm. Containers were installed at the end of each flume to intercept a portion of the runoff to determine nutrient loss. Samples were collected after every major rainfall event and immediately frozen in order to stabilize nutrients until preparation for chemical analysis. Nutrient accumulation and leaching were determined by deep soil sampling at previously described increments. Litter and fertilizer blend rates were determined as previously mentioned. The fall crops were broccoli and Elbon rye. Spring crops were sweet corn and sorghum-sudan. Rates were applied to fall fallow plots according to requirements of the following spring sweet corn crop.

METHODS: Texas, Fall 1993.

Treatments were applied to plots on 9 Sept. The 1X litter rate for broccoli and Elbon rye was 8.9 Mg/ha (4.0 tons/ac). A litter rate of 5.4 Mg/ha (2.4 tons/ac) was applied to fall fallow plots for sweet corn production the following spring. Litter rates for broccoli, rye, and fallow production were compared to a fertilizer blend of 67.0N-26.2P-34.9K, 67.0N-10.9P-37.3K, and 40.2N-8.7P-20.7K kg/ha respectively.

Broccoli transplants were hand-planted on 11 Sept. and spaced 30 cm apart in the row. Plots were harvested on 6 and 9 Nov. Elbon rye was seeded at the same rate as in objective 2 on 24 Sept. and harvested on 1 Dec. Soil samples were obtained on 24 March for all treatments.

METHODS: Texas, Spring 1993.

Treatments were applied to plots on 19 April. The 1X litter rate for sweet corn was 6.9 Mg/ha (3.1 tons/ac) and sorghum-sudan 7.8 Mg/ha (3.5 tons/ac). Fertilizer blend was applied at rates of 45.0N-2.5P-23.2K and 45.2N-6.5P-29.0K kg/ha for sweet corn and sorghum-sudan respectively.

Sweet corn and sorghum-sudan were seeded on 22 April and 10 May, respectively. Sweet corn was harvested on 7 July and sorghum-sudan on 16 June and 6 July. Run-off and leachate was collected after two major rainfall events. Soil samples were obtained on 22 July for all treatments.

METHODS: Texas, Fall 1993.

Treatments were applied to plots on 17 Sept. The 1X litter rate for broccoli was 9.6 Mg/ha (4.3 tons/ac) and rye 8.7 Mg/ha (3.8 tons/ac). Fallow plots received 8.7 Mg/ha (3.8 tons/ac). Fertilizer blend was applied at rates of 41.2N-24.4P-67.0K, 24.3N-7.3P-74.4K, and 41.2N-0.0P-41.8K kg/ha for broccoli, rye, and fallow plots respectively.

Broccoli was transplanted and Elbon rye seeded on 28 Sept. and 30 Oct., respectively. Broccoli was harvested on 3 Jan. and rye on 22 Nov., 6 Dec., and 4 Jan. Runoff and leachate samples were collected after 3 major rainfall events. Soil samples were obtained on 26 Jan. for all treatments.

METHODS: Texas, Spring 1994.

Treatments were applied to plots on 16 March. The 1X litter rate for sweet corn was 5.6 Mg/ha (2.5 tons/ac), sorghum-sudan 6.5 Mg/ha (2.9 tons/ac), and fall fallow plot 5.8 Mg/ha (2.6 tons/ac). Fertilizer blend was applied at rates of 45.0N-24.5P-27.9K, 28.1N-12.2P-18.6K, and 45.0N-19.5P-27.9K kg/ha for sweet corn, sorghum-sudan, and fall fallow plots, respectively.

Sweet corn was seeded on 22 March and sorghum-sudan on 25 April. Sweet corn was harvested on 14 June and sorghum-sudan on 2 June, and 19 July. Runoff and leachate samples were collected after 4 rainfall events. Soil samples were obtained on 26 July from all treatments.

OBJECTIVE 4: Demonstrations.

Locations: Texas – Oklahoma.

Texas: Demonstration plots were established in Texas in the spring and fall of 1993. Plots consisting of 0.8 ha each were established in three locations: Dr. Roderick Mitchell’s farm near Center Point, Texas in Camp Co.; Rusk Demonstration Farm near Rusk, Texas in Cherokee Co.; George Millard farm near Nacogdoches, Texas in Nacogdoches Co. All sites were acidic with very low N, moderate K and low P, Ca, Mg, Na, S and no salinity. The soils were deep sandy loam.

Agricultural-grade lime was applied to all plots at a rate of 4.5 Mg/ha (2 tons/acre). Strip plots were established with 15 m widths and 30 m lengths. Two of these plots running the length of the field were divided by a 4.5 m alley in order to divide the poultry litter plots and fertilizer blend plots. Treatments were applied according to N requirement for each crop.

OKLAHOMA: See attachment-Oklahoma Report.

Research results and discussion:

OBJECTIVE 1: Frequency X Litter Rate.

Location: TAES – Overton.

Mean yield of sweet corn produced on plots with continuous litter application showed a linear and quadratic response to increased rate (Table 1). Yields increased with a rate increase of 2 times the recommended. Rates of 4 times recommended had a tendency to decrease yield. Percent leaf concentration of major elements increased as rate increased. Increased litter rate decreased leaf concentration of Ca and Mg. However, the decrease in Mg was not significant. Frequency of application had no significant effect on any of the parameters measured. Comparable yield and nutrient uptake was found between fertilizer blend and the 1X rate.

Mean yield of broccoli produced on plots with continuous litter application showed no significant difference in yield (Table 2). This was probably due to a very high coefficient of variance between 1992 and 1993 planting. Yields from the fall 1993 plots were very low due to adverse weather conditions. The trend however, was the same as with sweet corn. Yield increased as rate increased up to 2X then decreased as rate reached 4X. Percent leaf concentration of major elements increased significantly as rate increased. Concentration of Ca decreased and Mg increased. However, applying rates of 4X in split application increased Ca leaf concentration. Frequency of application did not have any significant effect on any of the other parameters studied. Comparable yield and nutrient uptake was found between fertilizer blend and 1X rate.

At the conclusion of the first year cropping cycle (fall 1992), litter applied at 4X increased accumulation of NO3-N in the surface 15 cm of soil by 8.4 mg/kg when compared to 1X (Fig. 1). Leaching and accumulation at 122 cm depth from fertilizer blend was approximately 10 times that of the 1X treatment.

By the conclusion of the two year study (fall 1993) a slight accumulation of NO3-N was found in the surface 30 cm of soil. Leaching and accumulation was increased at 91 cm soil depth by both the 2X and 4X treatments as well as fertilizer blend.

At the conclusion of the first year study, a non-significant accumulation of residual P in the surface 15 cm of soil was found. Residual P increased as rate increased (Fig. 2). Fertilizer blend showed the least amount of accumulation.

Over time (fall 1993) residual soil P, in the surface 30 cm of soil increased dramatically as rate increased from 1X to 4X. There was a significant increase in P at the 61 cm depth from the 4X treatment. Fertilizer blend showed the least amount of accumulation.

Applying litter at 2 to 4 times the recommended rate increased K accumulation in the surface 30 cm of soil over the study period (Fig. 3). Little change in concentration from the 1X rate was found. There was inconsequential movement of K to lower depths of the soil profile.

Litter rate had a negligible effect on accumulation of Mg in the surface 30 cm of soil (Fig. 4). The most accumulation at lower depths was from fertilizer blend treatment.

Litter treatments tended to increase Ca concentration of the soil at depths below 15 cm (Fig. 5). Soil pH was maintained by litter treatment while fertilizer blend tended to decrease pH (Fig. 6).

All treatments decreased salt concentration in the surface 15 cm of soil but increased concentration at lower depths (Fig. 7). Lower concentrations were attributed more to the 1X treatment than all other treatments.

OBJECTIVE 2: Cropping System X Litter Rate X Time of Application.

Location: TAES – Overton, OSU – Bixby.

Over the three year study period it was found that cropping system had no significant effect on mean fruit weight or yield of tomatoes (Table 3). Fruit weight and yield were increased linear and quadratic by litter rate. The 1X litter rate produced the largest fruit while the 2X rate caused a decrease. Tomato fruit weight from fertilizer blend treatments was equal to those of the 1X litter treatment. Yield increased as litter rate increased. Both fruit weight and yield was increased from litter applied in both spring and fall.

There was an interactive effect between litter rate and season of application (Fig. 14). Tomato fruit weight was increased when 1X litter was applied in both spring and fall. A fall only application decreased fruit weight when compared to the 2X rate and fertilizer blend.

Turnip yield was not significantly affected by cropping system (Table 4). Yield was increased when litter was applied at the 1X rate ut decreased at 2X. Fertilizer blend produced yields equal to the 1X rate. Litter applied in both spring and fall produced yields greater than from other seasons of application. Yields from a fall application were greater than a spring only application. Turnip yields were higher when fertilizer blend was applied all seasons than when litter was applied in spring only.

Litter rate and season of application had an interactive effect on turnip yield (Fig. 15). Applying litter at 1X rate in both spring and fall and fall only increased yield. A spring only application of 1X decreased yield when compared to the other treatments.

Increasing litter rate increased sorghum-sudan yield but had no significant effect on rye yield (Table 5). Yield of sorghum-sudan was increased by litter application in both spring and fall and in the spring season in which the crop was grown. Applying fertilizer blend all seasons produced yields comparable to litter application in spring and fall and spring only.

When litter was applied in spring and fall and the fall season in which the crop was produced rye yield was increased. Yield was significantly increased by fertilizer blend applications in all seasons.

At the end of the first year (fall 1992) a slight increase in NO3-N in the surface 30 cm of soil was found (Fig. 8). Leaching and accumulation increased by the end of the study (fall 1994) as rate increased from 1X to 2X. The greatest increase was from fertilizer blend. Increases in accumulation of NO3-N in the control plots could be attributed to movement laterally from treated plots.

Cropping system influenced NO3-N leaching and accumulation (Fig. 9). At the end of the first year study (fall 1992) a system of spring vegetables followed by a fall cover crop showed less leaching of NO3-N than the other two systems. This trend followed through to the end of the study (fall 1994). The greatest amount of leaching and accumulation at the 122 cm depth was from a cropping system of a spring vegetable crop followed by a fall vegetable crop.

Season of application had an influence on NO3-N leaching and accumulation. (Fig. 10). At the end of the first year (fall 1992) fertilizer blend applied in both spring and fall showed the greatest amount of leaching and accumulation. By the end of the study (fall 1994) applications of both litter and fertilizer blend in both spring and fall showed increased leaching and accumulation. The least amount was from a single application applied in the spring or fall season.

Residual P accumulation was influenced by litter rates at the end of the first year (Fig. 11). Increasing the poultry litter application rate by 2X increased P accumulation in the surface 15 cm of soil. By the end of the study (fall 1994) P accumulation was increased by both litter rates. The least amount of P accumulation throughout the study was from fertilizer blend.

At the end of the first year (fall 1992) cropping system influenced residual soil P accumulation in the surface 15 cm of soil (Fig. 12). A cropping system of fall cover followed with a spring vegetable crop showed the greatest accumulation of P. By the end of the study (fall 1994) accumulation of P was increased by all cropping systems.

Season of application influenced residual P accumulation in the surface 15 cm of soil (Fig. 13). All seasons of application increased P accumulation over fertilizer blend treatments applied in both spring and fall. The greatest accumulation was when poultry litter was applied in both spring and fall. By the end of the study (fall 1994) all litter application treatments increased residual soil P. The least increase was from a spring only application.

Over the study period all litter rate treatments caused a decrease in soil K in the surface 30 cm (Fig. 16). The greatest increase was from the 2X rate at depths between 30-60 cm. Soil K concentration was not greatly affected by cropping system (Fig. 17). Applying litter in both spring and fall and fall only increased soil K at depths of 30-60 cm (Fig. 18).

Litter application rates had inconsequential effects on soil Ca concentration (Fig. 19). Calcium concentration in the surface 30 cm of soil was decreased by fertilizer blend. A cropping system of spring cover followed by fall vegetable increased soil Ca at depths of 30-60 cm (Fig. 20). The least amount of change in concentration was from a system of spring vegetables followed by fall vegetable. Below 30 cm depth, season of application had little effect on Ca concentration (Fig. 21).

Regardless of fertilizer treatment, Mg concentration decreased over time (Fig. 22). Concentration was decreased by all cropping systems (Fig. 23) but increased by all seasons of application (Fig. 24). There was a slight increase in concentration below 30 cm from fertilizer blend applied in all seasons.

Soil pH was decreased at all depths by litter treatment (Fig. 25). The largest decrease in the surface 30 cm of soil was from fertilizer blend. A system of spring vegetable followed by fall vegetable decreased soil pH over time more than the other systems (Fig. 26). Fertilizer blend applied all seasons produced the largest decrease in pH (Fig. 27).

Salt concentration was increased at all depths below 30 cm by litter and fertilizer blend (Fig. 28). Even though increased litter rate increased salt concentration, the most pronounced was from fertilizer blend. A system of spring vegetables followed by a fall cover crop showed considerably less salt concentration than the other two systems (Fig. 29). Applying litter in both spring and fall increased salt concentration (Fig. 30). The least was from a spring only application. Over the study period salt concentration at the lower depths was greatly increased by fertilizer blend.

Objective 2-Oklahoma: See attachment-Oklahoma Report.

OBJECTIVE 3: Leaching and Run-off.

Location: TAES-Overton.

At the end of the first season (fall 1992) of a three year study there was very little leaching of NO3-N (Fig. 31). The greatest accumulation from leaching was at the 122 cm depth from a poultry litter application of 4X. At the end of the study (spring 1994) a greater amount of leaching occurred from litter applications of 4X and fertilizer blend. The least amount of leaching was when poultry litter was applied 1X.

Cropping system had an effect on NO3-N leaching (Fig. 32). At the end of the first season (fall 1992) soil samples showed that a system of spring vegetables followed by leaving the soil fallow in the fall increased the incidence of NO3-N leaching. By the end of the study (spring 1994) a fall fallow system greatly increased leaching. The least amount of leaching was from a system of spring vegetables followed by a fall cover crop.

Poultry litter application rate had an effect on residual soil P (Fig. 33). Phosphorus accumulated in the surface 15 cm of soil but did not leach beyond the 30 cm depth. Applying poultry litter at 4X increased residual soil P. By the end of the study (spring 1994) accumulation of P was greatly increased by application rate of 4X. No increase in accumulation of P was found when fertilizer blend was applied. After two years there was no leaching of P below 30 cm of soil surface from any treatment.

Accumulation and leaching of residual P was influenced by cropping system (Fig. 34). At the end of the first cropping season (fall 1992) an increase in P was found in the surface 15 cm of soil from a system of spring cover crop followed by a fall vegetable. By the end of the study (spring 1994) this system had increased residual soil P drastically. No leaching of P below 30 cm of soil surface was observed for any treatment.

Over the two year study period concentration of K increased in the surface 60 cm of soil but decreased at deeper depths (Fig. 35).

All cropping systems increased soil Ca (Fig. 36). The least amount of acumulation at depths below 30 cm was from a system of spring cover followed by a fall vegetable. Cropping systems had little effect on Mg concentration (Fig. 37).

Regardless of cropping system used there was little effect on soil pH over the two year study period (Fig. 38).

Salt concentration in the surface 30 cm of soil was increased by all cropping systems (Fig. 39). Concentration was found to be higher in the surface 30 cm from a system of spring vegetables followed by fall cover and spring vegetables followed by fall fallow. A system of spring vegetables followed by a fall cover crop showed less leaching of salts than the other two systems.

As of spring 1993 negligible amounts of N from runoff were found from any cropping system (Fig. 40). A system of spring cover followed by fall vegetables and spring vegetables followed by fall fallow showed an almost two-fold increase in leached NO3-N at the 122 cm depth when compared to a system of spring vegetables followed by a fall cover crop.

Phosphorus concentration was almost nil in the run-off and leachate samples collected (data not shown).

Run-off and leachate samples collected in fall 1993 and spring 1994 have been frozen and will be analyzed as time permits. The findings will be reported at grower and professional meetings as well as field day reports and journal publications.

OBJECTIVE 4: Demonstrations.

Locations: Texas-Oklahoma.

Texas: In spring 1993, treatments were applied and plots power tilled and bedded. Plastic mulch was applied to individual beds with drip line placed beneath for irrigation. Transplants of tomatoes, watermelons, and cantaloupe were hand planted at Mitchell’s farm. At the Rusk Demonstration Farm cantaloupes were seeded. In fall 1993, the Rusk farm and Millard farm at Nacogdoches were planted to broccoli and turnips.

Conclusions

Objective 1: Frequency X Litter Rate.

Location: TAES – Overton.

Applying litter at no more than 2 times the recommended rate will result in significant yield increases of sweet corn. Major nutrient uptake will increase and minor elements such as Ca and Mg decrease. Poultry litter can be substituted for commercial fertilizer blends in sweet corn production resulting in equivalent yields. Broccoli yield can be maximized by applying poultry litter up to 2 times the recommended rate. Rates above this tend to decrease yield. Increasing litter rates increased uptake of all major elements as well as minor such as Mg, but decreased Ca. Results indicate that litter can be substituted for recommended fertilizer blend rates resulting in equivalent yields of both sweet corn and broccoli.

Poultry litter applied at recommended rates through soil testing will greatly reduce the incidence of NO3-N leaching and accumulation, thus reducing the incidence of ground water pollution. Applying litter over time, even at recommended rates increases residual P accumulation in the soil surface. Increasing the rates above recommended greatly increases the incidence of accumulation, thus increasing the risk of non-point source contamination of surface water.

Applying litter rates greater than recommended tends to increase K cancentration. Fertilizer blends tend to have more of an effect on Mg accumulation than poultry litter. Applying litter increases Ca concentration of the soil while maintaining soil pH. Fertilizer blends tend to decrease soil pH over time.

Objective 2: Cropping System X Litter Rate X Time of Application.

Location: TAES – Overton, OSU – Bixby.

Applying poultry litter by soil test results decreased NO3-N leaching, thus reducing the chance for ground water contamination. There is less risk of pollution from poultry litter applied by recommendations than from commercial fertilizer blend. A system of spring planted vegetables followed by a fall cover crop appears to be the system that can be recommended for reducing NO3-N leaching. This would be an easy system for growers to adopt. The majority of growers in East Texas, which is representative of the Southeastern U. S., plant only a spring vegetable crop. A single application of poultry litter either in the spring or fall will reduce the chance of NO3-N leaching thus reducing the risk of ground water pollution. Utilizing poultry litter as a fertilizer source, if applied according to Best Management Practices, will have less of an environmental threat to ground water pollution than the use of commercial fertilizer.

Poultry litter application rates based on N needs of the crop furnishes more P than can be used by the crop, thus creating conditions for surface water contamination. A systems approach, as far as using grass forage crops, does not appear to have any effect on reducing residual soil P. Regardless of season applied residual P from poultry litter will continue to accumulate in soil surface creating conditions for non-point source water pollution.

Applying litter greater than recommended increases soil K concentration while cropping system has little effect. Applications made in both spring and fall and fall only increases soil K concentration. Litter tends to maintain Ca concentration of the soil while fertilizer blend decreases concentration. The least amount of change in concentration of Ca is when spring vegetables are followed by fall vegetables. The season in which the litter is applied has little effect on soil Ca concentration. Magnesium concentration will decrease over time regardless of fertilizer treatment. Fertilizer blend decreases soil pH more than litter. Increased litter rate increases salt concentration of the soil but not as great as fertilizer blend. Utilizing a system of spring vegetables followed by a fall cover crop greatly reduces salt concentration. The least amount of concentration of salts can be found from a spring only litter application, while the greatest concentration, especially at lower depths, occurred when fertilizer blend is applied in all seasons.

Objective 3: Leaching and Run-off.

Location: TAES-Overton.

These data reaffirm previously discussed results from objective 1 and 2 that increasing litter rates above that recommended by soil testing can lead to conditions that are favorable for ground water contamination by NO3-N. Also that when litter is applied according to soil tests there is less danger of ground water pollution over time than when commercial fertilizer is used. This study shows that utilizing a system of planting spring vegetables followed by a fall cover crop will help decrease the risk of ground water pollution from leached NO3-N. Leaving the soil fallow in the fall increases the risk of pollution.

Increasing the rate of litter applied increases P accumulation. Regardless of cropping system P continues to increase over time. Incorporation of litter appears to reduce the incidence of run-off of both NO3-N and P.
Potassium concentration increases as litter rate increases. The least amount of accumulation occurs when a spring cover is followed by a fall vegetable. Cropping systems have little effect on Mg concentration or soil pH. A cropping system of spring vegetables followed by a fall cover crop reduces salt leaching and accumulation.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:
Publications

Publications arising from this project to date are:

1. Earhart, D. R., V. A. Haby, and M. L. Baker. 1993. Utilizing poultry litter as a fertilizer: sweet corn yield, mineral nutrition, and soil chemistry. HortScience 28(5) 173.

2. Baker, M. L., D. R. Earhart, and V. A. Haby. 1993. Influence of poultry litter on tomato yield, nutrition, and soil chemistry. HortScience 28(5) 173.

3. Earhart, D. R., M. L. Baker, V. A. Haby, and F. J. Dainello. 1993. Use of broiler litter as fertilizer for sweet corn production. Res. Ctr. Tech. Rpt. 93-1 pgs. 7-8.

4. McCraw, Dean. 1993. Fertilizing watermelons with poultry litter. Proc. 9th. Annu. Okla. Hort. Indus. Show. pgs. 144-146.

5. Earhart, D. R., V. A. Haby, and M. L. Baker. 1995. Effect of cropping system on NO3-N concentration of surface run-off water and leachate from poultry litter application. Res. Ctr. Tech. Rpt. 95-2. (In press).

6. Earhart, D. R., V. A. Haby, and M. L. Baker. 1995. Cropping system and season of application of poultry litter affected residual soil P concentration. Res. Ctr. Tech. Rpt. 95-2. (In press).

7. Earhart, D. R., V. A. Haby, and M. L. Baker. 1995. Effect of poultry litter rate of application on residual soil NO3-N. Res. Ctr. Tech. Rpt. 95-2. (In press).

8. Earhart, D. R., V. A. Haby, and M. L. Baker. 1995. Effect of cropping system on residual soil P from poultry litter application. Res. Ctr. Tech. Rpt. 95-2. (In press).

9. Haby, V. A., D. R. Earhart, G. Evers, and M. L. Baker. 1995. Land application of poultry litter in East Texas. Invited Tech. Poster. Paper to be published in Proceedings: Innovations and New Horizons in Livestock and Poultry Manure Management Conference. Meeting to be held in Austin, Texas. Sept. 6-7, 1995.

With the end of the study and all data analysis arriving at completion, future publications in major journals as well as Extension guides, circular’s, and pamphlets are being planned. These publications will be a collaborative effort between all cooperators involved.

Education & Outreach

Videos have been made at the Center’s test plots and on farm demonstration plots. These videos are available to Extension agents in order to provide them with information on how to establish research and demonstration plots within their respective counties.

A slide set on poultry litter applications for growing vegetables has been established and used by Research and Extension personnel for training producers, county agents, and other interested personnel.

Results of the study have been presented to participants at local and state conferences on livestock management, and fruit and vegetable production. Information was presented at several ‘Waste Management Training Sessions’ involving county Extension agents and poultry producers. Problems and results were discussed with the public and 4-H participants at field days sponsored by the Research Center.

Due to work being done, this study allowed for an educational project on broiler litter use in container mixes to be awarded under the Director’s minigrant competitive program for $10,000 in 1993-1994. Yearly grants of $4,000 from the Lake Fork Creek Hydrologic Unit Project have been received for enhancement of broiler litter studies and to prepare publications and farm cropping system plans to help alleviate environmental problems for Northeast Texas counties.

A research proposal was accepted in 1994 for further funding by the Southern Region SARE/ACE program for $135,000. The new three year study, based on results from the previous study, is titled ” Managing Soil Phosphorus Accumulation from Poultry Litter Application through Vegetable/Legume Rotations”. This study will be a cooperative effort between Texas A&M University and Oklahoma State University.

Because of Marty Baker’s involvement in this SARE/ACE project he has been appointed to serve as a member of the National SERA-TF-7 (Sustainable Agriculture) Task Force. He has also been appointed as Co-Chair of the TAEX Waste Initiative Team.

Project Outcomes

Project outcomes:

Results of this study indicate a significant impact to sustainable agriculture. Poultry litter has been shown to be an excellent source of nutrients for crop production. If rates of litter are applied according to soil test results and litter nutrient content, yields can be maximized and environmental problems such as NO3-N leaching and accumulation minimized. Including cover crops in a vegetable production system has a positive effect on reducing NO3-N accumulation and leaching, thus reducing the incidence of ground water pollution. A systems approach of using cover crops in a vegetable production program reduces the risk of contamination of surface water and ground water by NO3-N. The information gained from this study will be beneficial to producers by helping them develop management plans that will qualify for Best Management Practices. Poultry producers will benefit by enabling them to dispose of a larger amount of waste product with less environmental impact.

There was one aspect that emerged from this study that could create a problem with the use of poultry litter as a fertilizer source. Regardless of litter rate applied or cropping system used, residual soil P continued to increase. This was most pronounced in the surface 0-15 cm (0-6 in) of soil. This is the zone most susceptible to run-off, thus increasing the risk of non-point source pollution of surface water.

Legumes are able to use significant amounts of P. An advantage of using legumes for removing excess P is that no additional N fertilizer has to be applied since legumes can obtain N from the atmosphere through N2 fixation. A study was initiated this spring (1995) to evaluate the use of warm- and cool-season legumes in rotational vegetable cropping systems to remove excess P supplied by poultry litter.

Farmer Adoption

Cooperative Efforts

Texas A&M University and Oklahoma State University entered into a cooperative effort to research the environmental and economic aspects of utilizing poultry litter in vegetable production systems. The systems studied involved litter rate and vegetable-cover cropping systems. The responsibility of Texas A&M personnel was to evaluate litter application rate and frequencies as well as cropping systems and their effects on nutrient accumulation, leaching and run-off. That of Oklahoma State was to evaluate litter in cropping systems and their effect on nutrient accumulation and leaching. Both organizations had the responsibility for demonstrating litter use by commercial vegetable growers under grower conditions.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.